I will make notice of things I usually bypassed...
creating a text file named steam_appid containing only your appid(nothing else) inside "content" Folder.
{content folder is located inside your sdk..}
once you download the apropriate nwjs make sure you unzip all your NWJS export from construct ( Desktop folder ) then => in content(folder) where all the files of your game should be placed.... replace your game current .exe with the nwjs you downloaded from the website...
dont forget to add the dlls inside package.
I noticed the NWJS version you should be using is 0.60 and the sdk version is 1.50...
Oh yeah since we need sdks??? Maybe you shouldnt be uploading a zip file... but using the prompt command or even using the executable that automates everything found inside your sdk...